Ruthenium based complexes

ABSTRACT

The present invention relates to the field of catalysis and, more particularly, to a ruthenium carbonate complex of formula [Ru(diene)(C0 3 )] or [Ru(diene)(C0 3 ) 2 ]M n , wherein M is an alkaline (n is 2) or alkaline earth (n is 1) cation. The invention relates also to the use of said ruthenium carbonate complex as precursors for a number of Ru carboxylate complexes. Said specific ruthenium complexes possess a number of important advantages over the similar prior art known precursors.

TECHNICAL FIELD

The present invention relates to the field of catalysis and, more particularly, to a specific type of ruthenium carbonate complexes, as well as their preparation, as useful precursors for a number of Ru carboxylate complexes. Said specific ruthenium complexes possess a number of important advantages over the similar prior art known precursors.

PRIOR ART

Some ruthenium carboxylate complexes of general formula [Ru(diene)(OOCR)₂]_(n), with n equal to 1 or 2, have been described as useful starting compounds for the preparation of a number of ruthenium-diphosphine (PP) complexes of formula [Ru(PP)(OOCR)₂], which are good catalysts for the hydrogenation of carbon-carbon double bonds (e.g. see. O. Albers et al. J. Organomet. Chem, 1984, C62, 272; Ohta T. et al. in J. Org. Chem., 1987, 52, 3174-3176; Noyori R. et al. in J. Am. Chem. Soc., 1986, 108, 7117-7119; or Takaya H. et al. in Am. Chem. Soc., 1987, 109, 1596-1597).

Despite their usefulness, only indirect synthesis (i.e. more than one step) of said [Ru(diene)(OOCR)₂]_(n) from [(diene)RuCl₂]_(n) (which is one of the most common commercially available starting materials) is described in the literature. Indeed, the reported preparations of [Ru(diene)(OOCR)₂]_(n) require as intermediates of type [(diene)Ru(methylallyl)₂], as shown in the following scheme:

This way, the preparation of some complexes of type [(diene)Ru(OOCR)₂]_(n), wherein diene is COD or NBD, and R is CF₃, CCl₃, CHCl₂, CH₃ or some aryl, has been described (see H. Doucet et al., Tetrahedron Asymmetry, 1996, 7, 525-528; B. Heiser et al., Tetrahedron Asymmetry, 1991, 2(1), 51-62; M. O. Albers et al., Inorganic Syntheses, 1989, 26, 249-58; or M. O. Albers et al. J. Organomet. Chem, 1984, C62, 272).

The synthetic pathway described in those publications suffers from the following major drawbacks:

-   -   the synthesis of the allyl intermediates, such as         [(diene)Ru(bismethylallyl)₂], obtained from [Ru(diene)Cl₂]_(n),         is very diluted and requires the use of a Grignard reagent and         the intermediates obtained are only mildly stable, in both         solution and solid state, thus complicating an industrial         implementation of such synthetic operations;     -   the preparation of [Ru(diene)(OOCR)₂]_(n) with the prior art         method requires at least two steps starting from [Ru(diene)Cl₂],         and requires the formation of an intermediate difficult to         handle;     -   methylallyl ligand displacement by protonation is shown only         using halo acetic acids or some aryl carboxylic acids, i.e this         method is not general;     -   [(COD)Ru(acetate)₂] could not be obtained directly from the         bis-methylallyl complex and had been synthesized from         [(COD)Ru(OOCCF₃)₂]₂ by anionic ligand exchange with acetate         salts, adding thus an additional step to the overall process.         Moreover the overall yield of its preparation is quite poor.

Therefore there is a need for an improved process for obtaining complexes of type [(diene)Ru(OOCR)₂]_(n), wherein the intermediates of type [(diene)Ru(bismethylallyl)₂] are not required.

DESCRIPTION OF THE INVENTION

We have now surprisingly found that the complexes [(diene)Ru(OOCR)₂]_(n) can be directly obtained, in one step, from a new precursor, in the form of a Ru carbonate complex, by reacting said precursor with a carboxylic acid under specific convenient and highly productive reaction conditions.

In order to overcome the problems aforementioned, the present invention relates to a process for the preparation of a compound of formula

{[(diene)Ru(OOCR¹)₂]_(n)(H₂O)_(v)}  (I)

-   -   wherein n is 1 or 2;     -   v is 0 or 1;     -   “diene” represents a linear or branched C₄-C₁₅ hydrocarbon         compound comprising two carbon-carbon double bonds or a cyclic         C₇-C₂₀ hydrocarbon group comprising two carbon-carbon double         bonds; and     -   R¹ represents:         -   a hydrogen atom;         -   a pyridyl group;         -   a phenyl group optionally substituted by one to five halogen             atoms and/or C₁₋₄ alkyl or alkoxyl groups; or         -   a C₁₋₁₈ alkyl or alkenyl, optionally halogenated, and             optionally comprising:             -   one or two phenyl group, each phenyl group being                 optionally substituted by one to five halogen atoms                 and/or by C₁₋₄ alkyl or alkoxyl groups; and/or             -   one or two OH, amino, ether or thioether functional                 groups;                 comprising the step of reacting a precursor compound of                 the formulae

-   -   wherein “diene” has the same meaning as defined in formula (I),         M is an alkaline (n is 2) or alkaline earth (n is 1) cation;         in the presence of a carboxylic acid R¹COOH, wherein R¹ is as         defined above.

For the sake of clarity, by the expression “halogenated” it is meant that said group may be perhalogenated, i.e. all hydrogen atoms are replaced by halogen atoms, or partially halogenated, in particular may comprise from one to 5 halogen atoms such as Cl or F.

For the sake of clarity, it has to be mentioned that compound (I) comprises complexes having various structures, that is to say monomers wherein each R¹COO group is coordinated to only one Ru (i.e. [(diene)Ru(OOCR¹)₂]), or dimers wherein at least one of the R¹COO groups is coordinated to two Ru (e.g. [(diene)Ru(OOCR¹)(μ-OOCR¹)]₂ or [((diene)Ru(μ-OOCR¹)₂]₂).

For the sake of clarity, it has to be mentioned that by the expression “hydrocarbon compound comprising two carbon-carbon double bonds”, used in the definition of diene, it is meant a neutral ligand and not an allylic ligand.

According to a particular embodiment of the invention, said “diene” is a C₇-C₁₂, or a C₇-C₁₀, hydrocarbon compound comprising two carbon-carbon double bonds, optionally substituted, e.g. a cyclic C₇-C₁₂, or a C₇-C₁₀, hydrocarbon compound comprising two carbon-carbon double bonds. As well understood by a person skilled in the art, by “cyclic hydrocarbon” it is understood a compound comprising a cyclic moiety.

As non-limiting examples of suitable “diene” one may cite compounds such as COD (cycloocta-1,5-diene) or NBD (norbornadiene), 2,4-dimethyl-1,3-pentadiene or yet cyclohepta-1,4-diene.

The examples of “diene” provided above are applicable for both compounds (I) and (II). Anyhow, as a person skilled in the art would recognise, the diene present in the precursor (II) will be the same as the one of the compound (I) obtained by the present invention.

Another constituent of compound (I) is the carboxylic group R¹COO. The compounds of formula (I) can be monomeric (n=1), or dimeric (n=2) depending mainly on the exact nature of the group R¹, e.g. when R¹ is a methyl group the compound is monomeric while when R¹ is CCl₃ the compound is dimeric. In some cases said compound (I) may exist in the two forms (monomeric and dimeric).

According to a particular embodiment of the invention, said R¹ group represents:

-   -   a C₁₋₁₂ alkyl group, optionally halogenated, and optionally         comprising:         -   one phenyl group optionally substituted by one to five             halogen atoms and/or by C₁₋₄ alkyl or alkoxyl groups; and/or         -   one OH, amino or ether functional group;         -   or     -   a phenyl group optionally substituted by one to five halogen         atoms and/or by C₁₋₄ alkyl or alkoxyl groups.

According to a particular embodiment of the invention, said R¹ represents a C₂₋₁₀ alkyl group, optionally branched in the α and/or β position.

According to another particular embodiment of the invention, said R¹ is a group R² representing a branched C₂₋₁₀ alkyl group comprising in the α position a tertiary or quaternary carbon atom and/or in the β position a quaternary carbon atom and said R² optionally comprising one OH, amino or ether functional group, and also optionally comprising one phenyl group, the phenyl group being optionally substituted by one to five halogen atoms and/or by C₁₋₄ alkyl or alkoxyl groups.

For the sake of clarity, by the expression “α position” it is meant the usual meaning in the art, i.e. the carbon atom directly bound to the COO moiety of the group R²COO. Similarly by the expression “β position” it is meant a carbon atom directly bound to the α position.

According to a particular embodiment of the invention, the optional substituents of the phenyl group in the above embodiments are one, two or three halogen atoms, such as Cl and/or F, and/or C₁₋₄ alkyl or alkoxyl groups.

The examples of group R¹ provided above are applicable for both compound (I) and compound R¹COOH. Anyhow, as a person skilled in the art would recognise, the group R¹ present in compound R¹COOH will be the same as the one of the compound (I) obtained by the present invention. The same applies to the group R², in which case the carboxylic acid will be of formula group R²COOH.

As non-limiting examples of suitable R¹COOH, or R²COOH, and consequently of the R¹COO group of (I), or respectively R²COO, one may cite the following acids: acetic, the mono-, di-, tri-chloroacetic, propionic, isobutyric, pivalic, ^(t)Bu-acetic, 2-Et-hexanoic, cyclohexanecarboxylic, picolinic, cinnaminic, benzoic, 4-Me-benzoic, 4-OMe-benzoic, 3,5-dichloro-benzoic, isovaleric, 1-adamantanecarboxylic or sec-butyric acid.

The process of the invention is advantageously carried out in the presence of a solvent, especially in the case where the compound R¹COOH is not itself a liquid which could be used as diluent of the medium. It is also well understood by the person skilled in the art that said solvent is a liquid with a melting point below the reaction temperature. In the present invention, the exact nature of the solvent is not a critical element; however, as a person skilled in the art known, the choice of the solvent can be influenced by practical consideration such as the selective solubility of only one of the invention's process products (e.g. the compound of formula (I) or the salts formed such as R¹COOM, if M is an alkaline cation).

According to a particular embodiment of the invention, as typical examples of said solvent one may cite the following ones:

water;

C₁₋₅ alcohols, in particular methanol, ethanol, propanol or iso-propanol;

C₄₋₈ ethers, in particular tetrahydrofurane, methyl ter-butyl ether or dibutyl ether;

C₆₋₉ derivatives of benzene, in particular toluene, xylene, anisol or p-cymene;

-   -   C₃₋₉ esters, in particular methyl, ethyl, isopropyl or butyl         acetate; and

mixtures thereof.

Particularly appreciated solvents are water, C₁₋₃ alcohols such as methanol, C₄₋₆ ethers such as tetrahydrofurane or mixtures thereof.

The process of the invention as mentioned can be carried out in a broad range of temperature. According to a particular embodiment of the invention, the temperature is comprised between 10° C. and 100° C., more preferably between 20° C. and 70° C. Of course, a person skilled in the art is also able to select the preferred temperature as a function of the melting and boiling point as well as of the specific properties of said solvent as well as the desired time of reaction or conversion.

The process of the invention can be carried out under an inert or an oxygen containing atmosphere. As a person skilled in the art knows, the exact nature of the atmosphere depends on many factors such as the stability of products used or generated during the process towards oxygen. According to an embodiment of the present invention, it is preferable to carry out the process under an inert atmosphere (such as a nitrogen or argon atmosphere). However in many cases, for example when it is used a carboxylic acid of formula R²COOH, the nature of the atmosphere is indifferent, for instance it can be used an inert atmosphere, or an oxygen containing atmosphere (e.g. any mixture of an inert atmosphere and oxygen, such as for example air).

Typical manners to execute the invention's process are reported herein below in the examples.

The precursor (II) or (II′) is a novel compound and presents a number of advantages. Indeed this compound (II) or (II′), to the contrary of the prior art as [(diene)Ru(bismethylallyl)₂], is very stable towards hydrolysis and oxygen, as well as a number of other parameters. Compound (II) or (II′) is also more reactive compared to [(diene)Ru(bismethylallyl)₂], in particular towards aliphatic carboxylic acids, allowing then direct preparation of a greater diversity of compounds [Ru(diene)(OOCR)₂]_(n). Therefore its use in the above described process allows to solve many of the drawbacks mentioned about the prior art process to produce [Ru(diene)(OOCR)₂]_(n) complexes.

Therefore, another object of the present invention concerns the compounds of formula

wherein “diene” has the same meaning as defined in formula (I), M is an alkaline (n is 2) or alkaline earth (n is 1) cation.

According to a particular embodiment of the invention, M represents a sodium, potassium, cesium, calcium, stronzium or barium cation. In particular M is a sodium, potassium or cesium cation.

According to a particular embodiment of the compound (II), said compound is [Ru(COD)(CO₃)₂]Na₂; [Ru(COD)(CO₃)₂]K₂; [Ru(COD)(CO₃)₂]Cs₂; [Ru(NBD)(CO₃)₂]Na₂; [Ru(NBD)(CO₃)₂]K₂ or [Ru(NBD)(CO₃)₂]Cs₂ or [Ru(COD)(CO₃)].

It is also understood that the compounds of formula (II) can be in a solvated form, i.e. comprising a solvent coming from the reaction medium of their preparation, or as a mixed co-precipitated salt, i.e. comprising other salts which are obtained by product of their synthesis. This is a standard knowledge of the person skilled in the art and is well exemplified in the examples herein below.

Said compound (II) or (II′) can be obtained by reacting [Ru(diene)(Cl)₂] with a suitable alkaline or alkaline earth carbonate, in a suitable solvent such as a polar aprotic solvent and under an inert atmosphere, such as one defined in the above embodiments. The exact nature of the compound obtained (i.e. (II) or (II′)) is depending on the molar ratio between the [Ru(diene)(Cl)₂] and the carbonate.

As well understood by a person skilled in the art, by “polar aprotic solvent” it is understood that said solvent has a pK_(a) above 18 and a dielectric constant ∈ above 20, said constant being measured at standard conditions. Said constants can be retrieved in chemical Handbooks such as “Handbook of Chemistry and Physics”, 87^(th) edition, 2006-2007, page 15-13 to 15-23, ISBN 978-0-8493-0487-3, or such as March's “Advanced Organic Chemistry” 5^(th) edition, ISBN 0-471-58589-0, or any other similar reference.

It is also well understood by the person skilled in the art that said solvent is a liquid with a melting point below the reaction temperature. It is also useful to mention that another advantage of the invention's process is that the solvent used does not need particular requirements concerning the water contents, e.g. does not need to be anhydrous, fact that simplifies significantly any industrialisation of said process. In particular a technical grade solvent can be used, e.g. which may contain up to 1 or 2% w/w water.

As typical example of said solvent, one may cite solvents such as C₂₋₁₂ amides, in particular C₃₋₈ N-alkyl or N,N-dialkyl amides (e.g. acetamide, N,N-dimethyl-acetamide, N,N-dimethyl-formamide, N-acetyl piperidine or N-acetylpyrrolidine); C₆₋₉ N-alkyl lactame (e.g. N-methylpyrrolidone); C₄₋₈ carbamates or ureas (e.g. tetramethylurea); or mixtures thereof.

Particularly appreciated solvents are C₃₋₈ N,N-dialkyl amides (N,N-dimethyl-formamide or N,N-dimethyl-acetamide), or C₅₋₁₀ lactams (N-methylpyrrolidone).

The process for the preparation of compound (II) or (II′) can be carried out in a broad range of temperature. According to a particular embodiment of the invention, the temperature is comprised between 10° C. and 100° C., more preferably between 20° C. and 70° C. Of course, a person skilled in the art is also able to select the preferred temperature as a function of the melting and boiling point, as well as of the specific properties of said solvent, and of the desired time of reaction or conversion.

Typical manners to execute the invention's process are reported herein below in the examples.

EXAMPLES

The invention will now be described in further detail by way of the following examples, wherein the temperatures are indicated in degrees centigrade and the abbreviations have the usual meaning in the art.

All reagents and solvents were used as purchased in technical grade without further purification. NMR spectra were recorded on a Bruker AM-400 (¹H at 400.1 MHz, ¹³C at 100.6 MHz, and ³¹P at 161.9 MHz) spectrometer and normally measured at 300 K, in CD₂Cl₂ unless indicated otherwise. Chemical shifts are listed in ppm, and coupling constant in Hz. IR spectra were recorded on a Perkin Elmer FT-IR spectrometer, and the frequencies are given in cm⁻¹.

Example 1 Preparation of Complexes [(diene)Ru(CO₃)₂]M₂ Synthesis of {[(COD)Ru(CO₃)₂][Na]₂}2(NaCl) by Direct Reaction of Polymeric [(COD)RuCl₂]_(n) with Na₂CO₃

Sodium carbonate (189 g, 1.79 mol) was added at room temperature to a suspension of [(COD)RuCl₂]_(n) (200.0 g, 0.71 mol) in DMF (800 g). The reaction mixture was stirred at 40° C. for 20 hours during which time a solid precipitated out. The reaction mixture was then cooled down to room temperature and the solid formed was collected by filtration. The solid was washed with DMF (100 ml), with Et₂O (200 ml) and dried under vacuum (305 g, yield=87%).

IR (neat) ν: 3000-2800 (w); 1538 (s); 1321 (s).

¹H-NMR (D₂O): 4.3 (m, 2H, CH); 2.9 (m, 2H, CH); 2.4 (m, 2H, CH₂); 2.2 (m, 4H, CH₂); 2.0 (m, 2H, CH₂).

¹³C-NMR (D₂O): 170.6 (O—COO); 88.4 (CH); 86.6 (CH); 34.5 (CH₂); 28.9 (CH₂).

Synthesis of [(COD)Ru(CO₃)₂][Cs]₂: by Direct Reaction of Polymeric [(COD)RuCl₂]_(n), with Cs₂CO₃

Cesium carbonate (29 g, 89 mmol) was added at room temperature to a suspension of [(COD)RuCl₂]_(n) (10.0 g, 35.6 mmol) in DMF (40 g). The reaction mixture was stirred at 40° C. for 20 hours during which time a solid precipitated out. The reaction mixture was then cooled down to room temperature and the solid formed was collected by filtration. The precipitate was then extracted with MeOH in order to remove salts (such as the CsCl). The solution was evaporated to dryness and the residue was triturated with Et₂O (20 ml) to give a solid recovered by filtration and dried under vacuum (19 g, yield=90%).

IR (neat) ν: 3000-2800 (w); 1560 (s); 1270 (s).

¹H-NMR (D₂O): 4.3 (m, 2H, CH); 2.9 (m, 2H, CH); 2.4 (m, 2H, CH₂); 2.2 (m, 4H, CH₂); 2.0 (m, 2H, CH₂).

¹³C-NMR (D₂O): 170.7 (O—COO); 88.4 (CH); 86.6 (CH); 34.5 (CH₂); 28.9 (CH₂).

Synthesis of {[(NBD)Ru(CO₃)₂][Na]₂}2(NaCl) by Direct Reaction of Polymeric [(NBD)RuCl₂]_(n) with Na₂CO₃

Sodium carbonate (5.0 g, 47.3 mmol) was added at room temperature to a suspension of [(NBD)RuCl₂]_(n) (5.0 g, 18.9 mmol) in DMF (20 g). The reaction mixture was stirred at 40° C. for 20 hours during which time a solid precipitated out. The reaction mixture was then cooled down to room temperature and the solid formed was collected by filtration. The solid was washed with DMF (100 ml), with Et₂O (200 ml) and dried under vacuum (7.2 g, yield=80%).

IR (neat) ν: 3000-2850 (w); 1577 (s); 1334 (s).

¹H-NMR (D₂O): 4.54 (br. signal, 2H, CH); 3.90 (br. signal, 2H, CH); 3.69 (br. signal, 2H, CH₂); 1.59 (m, 2H, CH).

¹³C-NMR (D₂O): 178 (O—COO); 68.4 (CH); 65.1 (CH); 61.0 (CH₂); 52.9 (CH).

Synthesis of {[(COD)Ru(CO₃)}.(DMF) by Direct Reaction of Polymeric [(COD)RuCl₂]_(n) with Na₂CO₃

Sodium carbonate (117 g, 1.1 mol) was added at room temperature to a suspension of [(COD)RuCl₂]_(n) (200.0 g, 0.71 mol) in DMF (800 g). The reaction mixture was stirred at 40° C. for 24 hours during which time a solid precipitated out. The reaction mixture was then cooled down to room temperature and the solid formed was collected by filtration. The solid was washed several times with water in order to eliminate salts, with DMF (1×100 ml), with Et₂O (2×100 ml) and dried under vacuum (185 g, yield=70%).

Anal. Calcd for {[(COD)Ru(CO₃)}.(DMF), C₁₂H₁₉N₁O₄Ru: C, 42.10; H, 5.55; N, 4.09; Ru, 29.5. Found: C, 41.5; H, 5.85; N, 4.63; Ru, 28.9

IR (neat) ν: 3000-2800 (w); 1665 (s); 1546 (s); 1299 (s).

Example 2 Preparation of complexes [Ru(diene)(OOCR)₂]_(n) from the invention's carbonates Synthesis of {[(COD)Ru(O₂C^(t)Bu)]₂(μ-O₂C^(t)Bu)₂}: by Direct Reaction of {[(COD)Ru(CO₃)₂][Na]₂}2(NaCl) with Pivalic Acid in Water Under Nitrogen

Pivalic acid (8.7 g, 85 mmol) was slowly added at room temperature to a solution of {[(COD)Ru(CO₃)₂][Na]₂}2(NaCl) (10.0 g, 20.3 mmol) in water (40 g), under nitrogen. A yellow solid precipitated out which was washed with water (10 ml), with MeOH (10 ml) and dried under vacuum (6.0 g; yield=72%).

IR (neat): 2953.5 (m), 2950-2920 (w) 1568.1 (s); 1479 (s), 1406 (s).

¹H-NMR: 4.5 (m, 1H, CH); 4.3 (m, 1H, CH); 4.2 (m, 1H, CH); 4.0 (m, 1H, CH); 2.5 (m, 2H, CH₂); 2.3 (m, 2H, CH₂); 2.2 (m, 1H, CH₂); 2.1 (m, 1H, CH₂); 2.0 (m, 2H, CH₂); 1.12 (s, 9H, tBu); 1.11 (s, 9H, tBu).

¹³C-NMR: 194.5 (O—C═O); 191.9 (O—C═O); 97.9 (CH); 96.5 (CH); 88.5 (CH); 83.5 (CH); 41.6 (C); 40.9 (C); 30.3 (CH₂); 29.8 (CH₂); 28.4 (CH₂); 28.2 (CH₃); 28.1 (CH₂); 27.9 (CH₃).

Synthesis of {[(COD)Ru(O₂C^(t)Bu)]₂(μ-O₂C^(t)Bu)₂}: by Direct Reaction of {[(COD)Ru(CO₃)₂][Na]₂}2(NaCl) with Pivalic Acid in Water Under Air

Pivalic acid (8.7 g, 85 mmol) was slowly added at room temperature to a solution of {[(COD)Ru(CO₃)₂][Na]₂}2(NaCl) (10.0 g, 20.3 mmol) in water (40 g), under air. A yellow solid precipitated out which was washed with water (10 ml), with MeOH (10 ml) and dried under vacuum (6.2 g; yield=74%).

IR (neat): 2953.5 (m), 2950-2920 (w) 1568.1 (s); 1479 (s), 1406 (s).

¹H-NMR: 4.5 (m, 1H, CH); 4.3 (m, 1H, CH); 4.2 (m, 1H, CH); 4.0 (m, 1H, CH); 2.5 (m, 2H, CH₂); 2.3 (m, 2H, CH₂); 2.2 (m, 1H, CH₂); 2.1 (m, 1H, CH₂); 2.0 (m, 2H, CH₂); 1.12 (s, 9H, tBu); 1.11 (s, 9H, tBu).

¹³C-NMR: 194.5 (O—C═O); 191.9 (O—C═O); 97.9 (CH); 96.5 (CH); 88.5 (CH); 83.5 (CH); 41.6 (C); 40.9 (C); 30.3 (CH₂); 29.8 (CH₂); 28.4 (CH₂); 28.2 (CH₃); 28.1 (CH₂); 27.9 (CH₃).

Synthesis of [(COD)Ru(O₂CCH₃)₂] by Direct Reaction of {[(COD)Ru(CO₃)₂][Na]₂}2(NaCl) with Acetic Acid in Water Under Nitrogen

Acetic acid (5.1 g, 85.3 mmol) was slowly added at room temperature to a solution of {[(COD)Ru(CO₃)₂][Na]₂}2(NaCl) (10.0 g, 20.3 mmol) in water (40 g), under nitrogen. A solid precipitated which was collected washed with water (10 ml), cold MeOH (10 ml) and dried under vacuum to afford 4.9 g of product (yield=74%).

IR (neat): 3010-2800 (w); 1463 (s), 1395 (s).

¹H-NMR: 4.58 (m, 2H, CH); 3.2 (m, 2H, CH); 2.4 (m, 4H, CH₂); 2.2 (m, 2H, CH₂); 2.0 (2, 6H, CH₃ overlapped with m, 2H, CH₂).

¹³C-NMR: 190.6 (O—C═O); 89.3 (CH); 84.6 (CH); 31.4 (CH₂); 27.0 (CH₂).

Synthesis of [(COD)Ru(O₂CPh)₂] by Direct Reaction of {[(COD)Ru(CO₃)₂][Na]₂}2(NaCl) with Acetic Acid in Water Under Nitrogen

Benzoic acid (10.4 g, 85.3 mmol) was added portion wise at room temperature to a solution of {[(COD)Ru(CO₃)₂][Na]₂}2(NaCl) (10.0 g, 20.3 mmol) in water (40 g), under nitrogen. A solid precipitated which was collected washed with water (10 ml), cold MeOH (10 ml) and dried under vacuum to afford 7.1 g of product (yield=78%).

¹H-NMR: 8.1 (d, 4H, Ar); 7.6 (t, 2H, Ar); 7.4 (t, 4H, Ar); 4.8 (m, 2H, CH); 3.3 (m, 2H, CH); 2.5 (m, 4H, CH₂); 2.3 (m, 2H, CH₂); 2.1 (m, 2H, CH₂).

¹³C-NMR: 185 (O—C═O); 131.8 (CH); 131.4 (C); 128.7 (CH); 128.6 (CH); 89.5 (CH); 85.0 (CH); 33.2 (CH₂); 28.0 (CH₂).

Synthesis of {[(COD)Ru(O₂CCl₃)₂]₂.(H₂O)} by Direct Reaction of Polymeric [(COD)RuCl₂]_(n) with CCl₃COOH in Presence of a Base Under Nitrogen

Trichloroacetic acid (16.0 g, 98 mmol) was added at room temperature to a solution of {[(COD)Ru(CO₃)₂][Na]₂}2(NaCl) (10.0 g, 20.3 mmol) in water (40 g), under nitrogen. A solid precipitated which was collected washed with water (10 ml), cold MeOH (10 ml) and dried under vacuum to afford 9.2 g of product (yield=85%).

IR (neat): 3151 (b) (H₂O); 3000-2800 (w) (COD); 1648 (s) (COO); 1347 (COO).

¹H-NMR: 13.1 (H₂O); 4.98 (m, 2H, CH); 4.75 (m, 4H, CH); 4.65 (m, 2H, CH); 2.7-2.0 (series of m, 16H, CH₂).

¹³C-NMR: 175.3 (O—C═O); 174.0 (O—C═O); 99.8 (CH); 98.5 (CH); 95.0 (CH); 94.7 (overlapped CCl₃); 92.1 (CH); 87.5 (CH); 29.7 (CH₂); 29.3 (CH₂); 27.8 (CH₂); 27.7 (CH₂).

Synthesis of {[(COD)Ru(μ-O₂CEt)₄}: by Reaction of [(COD)Ru(CO₃)₂][Cs]₂ with Propionic Acid Under Nitrogen

Propionic acid (7.5 g, 101 mmol) was added at room temperature, under nitrogen atmosphere, to a suspension of [(COD)Ru(CO₃)₂][Cs]₂ (10.0 g, 16.9 mmol) in THF (50 ml). The reaction mixture was then heated to reflux and stirred under those conditions for 5 hours. It was then cooled down to room temperature and the precipitate was filtered off. The solution was evaporated to dryness and MeOH (30 ml) was added to give a crystalline solid which was collected by filtration and dried under vacuum (4.1 g, yield=68%).

¹H-NMR (CD₂Cl₂): 3.69 (broad s, 4H, CH); 2.58 (q, J=7.36 Hz, 4H, CH₂); 2.4 (m, 4H, CH₂); 2.16 (m, 4H, CH₂); 1.12 (t, J=7.36 Hz, 6H, CH₃).

¹³C-NMR (CD₂Cl₂): 184.6 (O—C═O); 87.2 (CH); 33.57 (CH₂); 28.2 (CH₂); 9.8 (CH₃).

Synthesis of {[(COD)Ru(O₂CAd)]₂(μ-O₂CAd)₂}: by Direct Reaction of {[(COD)Ru(CO₃)₂][Na]₂}2(NaCl) with 1-Adamantanecarboxylic Acid in Water Under Air

1-Adamantanecarboxylic acid (AdCOOH) (15.3 g, 85 mmol) was added at room temperature to a solution of {[(COD)Ru(CO₃)₂][Na]₂}2(NaCl) (10.0 g, 20.3 mmol) in water (50 g), under air. A yellow solid precipitated out which was washed with water (2×10 ml), with MeOH (2×5 mL) and dried under vacuum (10.6 g; 92%).

IR (neat): 2901 (s), 2848 (m) 1566 (s); 1392 (s).

¹H-NMR: 4.5 (m, 2H, CH); 4.3 (m, 2H, CH); 4.2 (m, 2H, CH); 4.0 (m, 2H, CH); 2.8-1.2 (series of m, 76H, CH+CH₂).

¹³C-NMR: 193.4 (O—C═O); 190.9 (O—C═O); 97.8 (CH); 96.5 (CH); 88.3 (CH); 83.3 (CH); 43.7 (C); 42.9 (C); 40.4 (CH); 40.0 (CH); 37.4 (CH); 37.2 (CH); 30.3 (CH₂); 29.8 to (CH₂); 29.2 (CH₂); 28.9 (CH₂); 28.4 (CH₂); 28.2 (CH₂).

Synthesis of [(COD)Ru(O₂CPh(o-OMe))₂] by Reaction of {[(COD)Ru(CO₃)₂][Na]₂}2(NaCl) with o-Methoxy Benzoic Acid in Water

o-Methoxy benzoic acid (12.9 g, 85 mmol) was added portion wise at room temperature to a solution of {[(COD)Ru(CO₃)₂][Na]₂}2(NaCl) (10.0 g, 20.3 mmol) in water (50 g), under nitrogen. A solid precipitated which was collected, washed with water (2×10 ml), cold MeOH (2×5 ml) and dried under vacuum to afford 7.9 g of product (76% yield).

¹H-NMR: 8.0 (m, 2H, Ar); 7.5 (m, 2H, Ar); 7.0 (m, 4H, Ar); 4.8 (m, 2H, CH); 3.9 (s, 3H, CH₃); 3.3 (m, 2H, CH); 2.4 (m, 4H, CH₂); 2.2 (m, 2H, CH₂); 2.1 (m, 2H, CH₂).

¹³C-NMR: 184.5 (O—C═O); 160.2 (C); 134.3 (CH); 131.9 (CH); 122.5 (C); 120.3 (CH); 112.5 (CH); 90.1 (CH); 85.5 (CH); 56.3 (OCH₃); 31.9. (CH₂); 27.5 (CH₂).

Synthesis of [(COD)Ru(O₂C^(t)Bu)₂] by Reaction {[(COD)Ru(CO₃}.(DMF) with Pivalic Acid

Pivalic acid (3.12 g, 30.6 mmol) was added at room temperature to a suspension of {[(COD)Ru(CO₃)}.(DMF) (5 g, 14.6 mmol) in THF (30 ml). After overnight stirring, the reaction mixture was evaporated to dryness and cold MeOH was added to give [(COD)Ru(O₂CtBu)₂] which was collected, washed with cold MeOH and dried under vacuum (3.5 g, 58%).

IR (neat) ν: 2959 (m), 2950-2920 (w); 1476 (s), 1492(s), 1426 (s).

¹H-NMR: 4.5 (m, 2H, CH); 3.2 (m, 2H, CH); 2.38 (m, 2H, CH₂); 2.3 (m, 2H, CH₂); 2.2 (m, 2H, CH₂); 2.08 (s, 2H, CH₂); 1.05 (s, 18H, tBu).

¹³C-NMR: 199 (O—C═O); 89.3 (CH); 85.7 (CH); 40.5 (C); 31.6. (CH₂); 27.7 (CH₂); 26.2 (CH₃).

Synthesis of [(COD)Ru(O₂CCH₂ ^(t)Bu)₂] by Reaction of {[(COD)Ru(CO₃)₂][Na]₂}2(NaCl) with t-Butylacetic Acid

t-Butylacetic acid (9.4 g, 81.2 mmol) was slowly added at room temperature to a solution of {[(COD)Ru(CO₃)₂][Na]₂}2(NaCl) (10.0 g, 20.3 mmol) in water (40 g), under nitrogen. A yellow solid precipitated out which was washed with water (1×10 ml), with MeOH (2×5 ml) and dried under vacuum (6.9 g; 77%).

¹H-NMR: 4.5 (m, 2H, CH); 3.2 (m, 2H, CH); 2.38 (m, 2H, CH₂); 2.3 (m, 2H, CH₂); 2.2 (m, 2H, CH₂); 2.08 (s, 2H, CH₂); 2.0 (m, 2H, CH₂); 1.05 (s, 18H, tBu).

¹³C-NMR: 192.8 (O—C═O); 89.3 (CH); 84.5 (CH); 51.6 (CH₂); 31.7. (CH₂); 31.2 (C); 29.9 (CH₃); 27.4. (CH₂). 

1. A process for the preparation of a compound of formula {[(diene)Ru(OOCR¹)₂]_(n)(H₂O)_(v)}  (I) wherein n is 1 or 2; v is 0 or 1; “diene” represents a linear or branched C₄-C₁₅ hydrocarbon compound comprising two carbon-carbon double bonds or a cyclic C₇-C₂₀ hydrocarbon group comprising two carbon-carbon double bonds; and R¹ represents: a hydrogen atom; a pyridyl group; a phenyl group optionally substituted by one to five halogen atoms and/or C₁₋₄ alkyl or alkoxyl groups; or a C₁₋₁₈ alkyl or alkenyl, optionally halogenated, and optionally comprising: one or two phenyl group, each phenyl group being optionally substituted by one to five halogen atoms and/or by C₁₋₄ alkyl or alkoxyl groups; and/or one or two OH, amino, ether or thioether functional groups; comprising the step of reacting a precursor compound of the formulae

wherein “diene” has the same meaning as defined in formula (I), M is an alkaline (n is 2) or alkaline earth (n is 1) cation; in the presence of a carboxylic acid R¹COOH, wherein R¹ is as defined in formula (I).
 2. A process according to claim 1, wherein the “diene” is a C₇-C₁₂ hydrocarbon compound comprising two carbon-carbon double bonds, optionally substituted.
 3. A process according to claim 1, wherein the R¹ group represents: a C₁₋₁₂ alkyl group, optionally halogenated, and optionally comprising: one phenyl group optionally substituted by one to five halogen atoms and/or by C₁₋₄ alkyl or alkoxyl groups; and/or one OH, amino or ether functional group; or a phenyl group optionally substituted by one to five halogen atoms and/or by C₁₋₄ alkyl or alkoxyl groups.
 4. A process according to claim 2, wherein the R¹ group represents a C₂₋₁₀ alkyl group, optionally branched in the α and/or β position.
 5. A process according to claim 2, wherein the R¹ group is a R² group representing a branched C₂₋₁₀ alkyl group comprising in the α position a tertiary or quaternary carbon atom and/or in the β position a quaternary carbon atom and said R² group optionally comprising one OH, amino or ether functional group, and also optionally comprising one phenyl group, the phenyl group being optionally substituted by one to five halogen atoms and/or by C₁₋₄ alkyl or alkoxyl groups.
 6. A process according to claim 1, wherein the R¹COOH, and consequently the R¹COO group of (I), is acetic, the mono-, di-, tri-chloroacetic, propionic, isobutyric, pivalic, ^(t)Bu-acetic, 2-Et-hexanoic, cyclohexanecarboxylic, picolinic, cinnaminic, benzoic, 4-Me-benzoic, 4-OMe-benzoic, 3,5-dichloro-benzoic, isovaleric, 1-adamantanecarboxylic or sec-butyric acid.
 7. A compound of formula

wherein “diene” has the same meaning as defined in formula (I), M is an alkaline (n is 2) or alkaline earth (n is 1) cation.
 8. A compound according to claim 7, characterised in that M represents a sodium, potassium, cesium, calcium, stronzium or barium cation.
 9. A compound according to claim 7, characterised in that it is [Ru(COD)(CO₃)₂]Na₂; [Ru(COD)(CO₃)₂]K₂; [Ru(COD)(CO₃)₂]Cs₂; [Ru(NBD)(CO₃)₂]Na₂; [Ru(NBD)(CO₃)₂]K₂ or [Ru(NBD)(CO₃)₂]Cs₂ or [Ru(COD)(CO₃)]. 